1. Field of the Invention
The present invention relates to a bar code reader, and more particularly to a portable, small-size hand-supported bar code reader.
2. Description of the Prior Art
Some portable hand-held scanning bar code readers employ a charge-coupled device (CCD) combined with an image-reducing optical system including a spherical lens. A light beam emitted by a light source is applied to a bar code, and reflected light from the bar code is reflected by a mirror and then focused by the spherical lens onto the CCD. The CCD converts the focused light into an electric signal whose intensity varies with time depending on the information represented by the bar code. The electric signal produced by the CCD is then amplified by an amplifier, converted into a binary signal by a binary signal generator, and decoded into a decoded signal by a decoder. The decoded signal is outputted from the bar code reader through an interface.
During use of such a portable hand-held scanning bar code reader, the operator is required to hold the bar code reader by hand. Since one hand of the operator is occupied by the bar code reader, the operator can only use the other hand or may have to pass the bar code reader to the other hand to do some other work. Therefore, the efficiency of the job which the operator performs while holding the bar code reader by hand is considerably low.
Attempts have been made to reduce the size of portable scanning bar code readers. One small-size portable bar code reader is disclosed in Japanese laid-open utility model publication No. 58-138157. The disclosed bar code reader is a pencil-shaped bar code reader that can be mounted on an operator's finger. The pencil-shaped bar code reader is relatively long, and suffers frequent reading errors because it is required to trace bar codes in order to read them. U.S. Pat. No. 4,766,299 discloses a hand-mounted bar code reader. The disclosed hand-mounted bar code reader is however relatively large in size as its housing accommodates a conventional laser and scanning mechanism for producing a scanning laser beam. U.S. Pat. No. 3,978,318 shows a hand-operated scanner that can be worn by an operator's finger. However, the disclosed hand-operated scanner is also relatively large in size, and must to be moved over a data bearing medium in order to read the data.
Furthermore, the optical system of the conventional scanning bar code readers has imposed certain limitations on efforts to make them smaller in size. Inasmuch as the scanning bar code readers have an image- reducing optical system including a spherical lens, as described above, if the focal length of the optical system between the bar code and the spherical lens is to be shortened to reduce the size of the bar code reader, then it is necessary to employ a smaller spherical lens with a reduced radius of curvature. The smaller spherical lens would however be unable to provide a light intensity strong enough to detect a bar code image on the CCD. Since the spherical lens is required to focus the reflected light from the bar code into a smaller bar code image on the CCD, the spherical lens should have a certain focal length that is necessary between itself and the CCD. Therefore, it has been impossible for scanning bar code readers to be greatly reduced in size because of those optical system limitations.